Torsional vibration excitation of steam engine

[rob768]

Is there anyone with information of the forces generated by a two cylinder (90 degrees crank angle) steam engine. This with regards to calculation of the torsional vibrations in a ship's propulsion installation.

 

[MikeHalloran]

Uh, probably not more than 300,000 of our members, but they'd need a little more detail than you've given so far.



Mike Halloran
Pembroke Pines, FL, USA

 

[rob768]

Ok, someone over here is building a combined steam/diesel driven ship (steam or diesel, not both at the same time) for which we have to perform the torsional vibration calculation (which has to be accepted by Lloyds). For the diesel part, this is not a problem, but translating steam pulses of a 2 cylinder compound steam engine to input data for a torsional vibration model is a bit out of the ordinary for me. In fact, it will be the first steam engine i will see working (apart from the occasional one in exhibtions or musea).
We have some info, as it seems my boss has done it before, but i would like to find out for myself (with a little help from my friends )

 

[ivymike]

Wouldn't you do it the same way? Calculate net gas force vs. time on the piston, calculate net inertia force vs time on the piston, calculate net torque vs time due to rod whipping, translate those into net torque vs. time at the crankshaft, break into half-orders of harmonic content, and apply to your mass-elastic system?

 

[rob768]

It'll probably come down to estimates based on that. Lack of data is our biggest problem (and my problem is that I can't do such calculations myself, so I have to ask others over here)